Don't skimp on the PSU it may be tempting to get that $100 850W PSU you see but it's not worth it. Quality is what you want here since it supplies the life blood of your system. A 650W from Corsair, Seasonic, or XFX should be enough to put you in optimal power efficiency when under 100% load. The 80+ power ratings do matter. Basically the lower 80+ ratings (Bronze) waste more energy converting from 120V AC power to the DC power and voltages you need. This wasted energy is converted to heat. So if you get an 80+Gold PSU it will use less energy and produce less heat. Should you get an 80+gold PSU? Probably not, 80+ gold is only suitable for those very energy conscious or if you're going to be running your system at 100% load 24/7(like a dedicated folding rig). Extra cables to buy? You shouldn't have to buy any extra cables with a PSU since usually PSUs have enough cables for what they are rated to power for example a 750W PSU can power 2 GPUs and therefore has 4 PCIe power connectors. However, sometimes if you're in a large case you may need to get extensions for some connections to do nice tidy cable management. Different models in the top brands usually don't have many differentiating features the most noted ones are modular vs non-modular and warranty length.